Strongly that could be it, but what if he isn't? Though most likely you are right, so far most of the family show up in this arc well all except one which I hope she will.

Spoiler for 57:

I really don't like the idea of Issa doing this of his own will, I mean seriously!? The real bad part is that if it were true, than he would be betraying Akasha and her trust as far as Alucard and protecting Moka is concerned, his position is more of a neutral/supporting character.